Since the earliest days of seafaring, increased speed of sailboats has been sought. In recent times, the demand for very high speed sailing craft by recreational sailors has created a large boatbuilding industry specifically to provide extremely fast sailing craft.
Previous efforts at the design of high speed sailboats have centered on one or more of the following steps to reduce the frictional and wave making resistance of the hull(s): vessel weight reduction, efficient hull forms (i.e., catamarans and planing hulls), or hydrofoils with which the hull is lifted out of the water. All of these methods have increased sailing speed to some extent. However, the most dramatic speed breakthrough in many years has been achieved by the sailboard. This vessel consists of a surfboard-shaped hull to which a freely pivoting mast and sail is attached. The sail is restrained only by the operator; see U.S. Pat. No 3,487,800 of Schweitzer and Drake (1970). A direct consequence of the "Free Sail System" of Schweitzer and Drake is that in strong winds the operator inclines the sail to windward, rather than allowing the sail to heel away from the wind as is the case with all conventionally rigged sailboats. Because the wind-induced force of a sail (or aerofoil) is always perpendicular to its surface, when the sailboard sail is inclined to windward it has a portion of this force directed upwardly against the downward force of gravity. This upward force lifts the hull partially (or even completely) out of the water, thereby reducing its fricitional and wave making resistance, and increased speed results.
This concept is well documented. There are examples of sailing vessels designed to utilize "lift" producing sails dating back to the 1800's.
Of all the previous attempts at "lifting sails", only the "Free Sail System" of Schweitzer and Drake allows the sail to swing about all three of the major axes, extending fore and aft, athwartships, and up from the deck. However, the mast is pivoted at its base about a socket in a fixed position on the deck. It is desirable that the said be readily pivotable about all three axes for the following reason. As the said is shifted to windward of the vessel, it causes an imbalance of forces commonly known as "lee helm", which is the tendency of the vessel to turn away from the wind. To correct this problem, the said must be tilted farther aft. This will bring the drive and drag producing forces back into equilibrium and the vessel will steer straight ahead.
The limiting condition of the "Free Sail System" is that it must be "substantially free from pivotal restraint", meaning that the operator actually holds the sail up against the wind without the help of any mechanical devices. This causes the sailboard to be very strenuous to operate and further confines its tri-axis control "lifting sail" concept to very small vessels with very small sails.
These developments have left unsolved the problem of how to obtain the benefits of a sail controllable about all three major axes in a manner suitable for use on larger, more stable sailing vessels.